Various methods are known in the prior art for the production of substituted or unsubstituted alkoxysilanes and alkoxypolysiloxanes. U.S. Pat. No. 3,792,071 discloses a continuous process of reacting chlorosilane with a substituted or unsubstituted alcohol and optional water in a reactor column equipped with a reflux condenser and kept at high temperatures. In this process, chlorosilane is admitted into the reaction column through its top and the alcohol in gas form is admitted into the column at or in proximity to its lower end, and water is admitted into the column at any desired position. An intermediate section in the column is kept at a temperature higher by at least 0.5.degree. C. than the boiling point of the alcohol, and excess alcohol boiling under reflux always exists at the column top throughout the reaction. The reaction product is withdrawn from the column through the lower end or from below the alcohol admission inlet.
This process is specially intended for the continuous production of alkoxysilanes. For example, an alkoxysilane is continuously produced by admitting methyltrichlorosilane and gaseous ethanol at 110.degree. C. into a reaction column heated at a temperature of 100.degree. C., thereby effecting reaction between these compounds at high temperatures, allowing a reaction product (alkoxysilane) to exit from the lower end of the column, and separating excess ethanol from the reaction product by distillation.
If it is desired to effect partial hydrolysis of methyltrichlorosilane concurrently in this process, methyltrichlorosilane is admitted as a triol solution and water is introduced as steam at a temperature of 105.degree. C. into the column below the silane inlet. This type of reaction, however, does not yield a well balanced high molecular weight reaction product, but rather a mixture of methylethoxypolysiloxane and methyltriethoxysiloxane. Additionally, the above-mentioned process uses solvent and feeds water in gas form, that is, steam. Such a steam conduit requires intense thermal insulation because otherwise, water can condense intermediate the conduit, failing to provide desired supply of water so that an alkoxysilane having a desired degree of hydrolysis is produced no longer. Also otherwise, gelation can occur in the supply conduit, failing to produce an end product.
U.S. Pat. No. 4,209,454 discloses a process for producing a polysiloxane having a hydrocarbon residue attached to silicon through oxygen by reacting a halogenosilane with alcohol and water in the presence of a desired polysiloxane, characterized by the steps of admitting alcohol, water, and an acidic catalyst capable of promoting condensation of a group to which a Si bond is condensible into a still equipped with a column and optionally, a reflux condenser and previously charged with the desired polysiloxane, in such amounts that there are present at least 5% by weight of the alcohol and 0.001 to 5% by weight of the catalyst based on the total weight of the alcohol, catalyst, and polysiloxane in the still, heating the contents of the still under reflux for boiling, introducing a halogenosilane to be reacted into the column at a position of at least 1 m above the column lower end, and continuously withdrawing the polysiloxane from the still as it is formed.
This process is an improvement over the first-mentioned process. Studying the process, the inventors have found the following problems. Since the alcohol is admitted into the still (or reactor) in such an amount that there is present at least 5% by weight of the alcohol based on the total weight of the alcohol, catalyst, and polysiloxane in the still as mentioned above, the reaction system becomes an alcohol excess system containing at least 5% by weight of alcohol. Then a substantial amount of the alcohol can be left in the reaction system and consequently, a substantial amount of a hydrogen halide by-product resulting from reaction of halogenosilane with alcohol can be left in the resulting polysiloxane. This is probably a result of the extremely high solubility of hydrogen halide in alcohol as compared with the low solubility of hydrogen halide in polysiloxane. In any case, the above.mentioned process becomes complicated since it requires an extra step of distilling off hydrogen halide along with alcohol by stripping, neutralization or the like. The use of a separate catalyst is disadvantageous in economy. There is a need for overcoming these problems.
U.S. Pat. No. 3,668,180 discloses a process for producing an alkoxyorganopolysiloxane comprising the steps of reacting an organohalogenosilane with water and a lower aliphatic alcohol in the presence of a hydrocarbon solvent in a first reactor between -10.degree. C. and +10.degree. C., and continuously introducing the resulting intermediate into a second reactor filled with a supplemental solvent where reaction is completed under reflux. This process also suffers from cumbersome operations associated with the use of solvent and two reactors.